In a mobile communication system, a CSG including multiple wireless resource management entities is always formed for a given user equipment (UE) group, so as to provide better services for the given UE group. For example, all UEs within a company or a school are a given UE group, and a CSG including multiple wireless resource management entities is formed for the UE group to provide special access services.
It is ubiquitous in a mobile communication system that multiple wireless resource management entities form the CSG for the given UE group. A long term evolution (LTE) system of system architecture evolution (SAE) is taken as an example to describe these clearly.
FIG. 1 is a schematic diagram illustrating a LTE system. As shown in FIG. 1, in the wireless access network of the LTE system, the wireless resource management entities includes evolved node B (eNB) 101, home eNB (HeNB) 102, and an optional HeNB GW 103. The eNBs 101 connect with each other via an X2 interface, each eNB 101 directly connects with a mobile management entity (MME) 104 in a core network via an 51 interface respectively; HeNB 102 may connect with HeNB GW 103 via the S1 interface, and HeNB GW 103 connects with MME 104 via the S1 interface; or HeNB 102 may directly connect with MME 104 via the S1 interface; or when there is no HeNB GW 103 in the system, HeNB 102 directly connects with MME 104 via the S1 interface. In addition, eNB 101 and HeNB 102 may both connect with multiple MMEs 104 in the core network.
In order to provide better access services, various wireless resource management entities are provided. Taking HeNB 102 in the LTE system of FIG. 1 as an example, there are HeNBs of an open type, HeNBs of a hybrid type and HeNBs of a CSG type. The UEs accessing the HeNB of the open type are not limited and any UE can access the HeNB of the open type; only UEs in a certain UE group (the UE in the certain UE group is called as CSG UE for convenience) served by the HeNB of the CSG type can access the HeNB of the CSG type; CSG UEs served by the HeNB of the hybrid type can access the HeNB of the hybrid type, so that better access services can be provided for the CSG UEs, meanwhile other non-CSG UEs also can access the HeNB of the hybrid type.
FIG. 2 is a flowchart illustrating a procedure that UE moves to a HeNB CSG or a HeNB hybrid cell by taking a S1 handover as an example. A source eNB may be a macro eNB or a HeNB. As shown in FIG. 2, the procedure includes the following operations.
In block 201: a source eNB (S-(H)eNB) configures UE to send a Proximity Indication control,
In block 202: when the UE reaches a CSG cell or a hybrid cell (a CSG ID of the cell is in a list of accessible CSGs of the UE), the UE sends a Proximity Indication of “entering” to an eNB. The Proximity Indication includes a radio access technology (RAT) and frequency information of the proximity cell.
In block 203: if measurement configurations of the frequency/RAT do not exist, the source eNB configures corresponding measurement for the UE, and the measurement may include a measurement interval. In this way, the UE can perform measurement of the reported RAT and frequency.
In block 204: the UE sends a measurement report to the eNB. The measurement report includes protocol control information (PCI) of the measured cell.
In block 205: the source eNB configures the UE to obtain and report System Information (SI) of a cell corresponding to given PCI.
In block 206: the UE obtains SI related to a target HeNB by using an automatic interval. In block 207: the UE sends a measurement report to the eNB. The message includes an E-UTRAN cell global identifier (ECGI), tracking area code (TAC), CSG ID and members of the target HeNB cell.
In block 208: the source eNB sends a handover requirement message to an MME. The message includes the ECGI and CSG ID of a target cell. If the target cell is in a hybrid access mode, the message includes a cell access mode.
In block 209: the MME performs access control for the UE according to the received CSG ID and the stored signed CSG information of the UE. After the access control is failed, the MME sends a handover preparing failure message to the source eNB to terminate this handover procedure. If the handover requirement message includes the cell access mode, the MME decides a member state of the UE and sends the member state to the target eNB via a handover request message.
In block 210: the MME sends the handover request message to a Target-HeNB. If HeNB GWs are deployed, the handover request message is sent to the target HeNB via the HeNB The message includes CSG ID. If the target cell is in a hybrid access mode, the message also includes a CSG member indication.
In block 211: the target HeNB determines whether the CSG ID in the received handover request message is the CSG ID broadcasted by the target cell. If yes, appropriate resources are assigned. If the CSG member indication indicating that the UE is the member, the target HeNB performs priority principle for the UE.
In block 212: the target HeNB sends a handover request acknowledgement message to the MME. If the HeNB GWs are deployed, the handover request acknowledgement message is sent to the MME via the HeNB GW.
In block 213: the MME sends a handover command message to the source eNB.
In block 214: the source eNB sends the handover command message to the UE, A RRC connection re-configuration message includes mobile control information.
In the procedure of moving to the CSG cell by the UE, the access control is implemented via two steps, the UE determines whether the UE is the member of the target cell according to the CSG ID of the target cell and the list of the accessible CSGs of the UE stored by the UE, and the UE reports that the UE is the member to the network. The MME further authenticates the UE in the block 209.
Thus, the conventional procedure for implementing that the UE moves to the HeNB via the S1 handover is finished.
When the target cell (not the CSG cell or the hybrid cell) supports radio access network (RAN) share, the source eNB selects one public land mobile network (PLMN) as a new PLMN registered by the UE according to an intersection of PLMNs supported by the target cell and accessible PLMNs of the UE.
If the target cell is the CSG cell supporting the RAN share, the target cell broadcasts multiple supported PLMN identifiers and CSG IDs. If (PLMN1, broadcasted CSG ID) is in the list of the accessible CSGs of the UE, the UE is the member. The PLMN1 is the PLMN broadcasted by the target cell and the PLMN1 also is a current registered PLMN (rPLMN) or equivalent PLMN (ePLMN) of the UE. When the UE is the member of the CSG cell, the UE reports the CGI, TAI, CSG ID and a member identity to the source eNB.
After receiving the report of the UE, the source eNB does not know the PLMNs supported by the target HeNB cell, and does not know the PLMNs of which the UE is the member either, and thus the source eNB can not select the target PLMN. If the target PLMN is not selected appropriately, the handover will fail and continuity of the UE services will be affected.
For example:UE rPLMN=B, ePLMN={A,C}, a list of accessible CSGs={(c1, A), (c1, B), (c2, A)}
The standby HO target cell broadcasts PLMNs {D, A, C, E}, CSG=c1
Because (c1, A) is in the list of the accessible CSGs of the UE, the UE will indicate the member identity to the source eNB. The source eNB does not know the PLMNs supported by the target cell, the source eNB can only know the first PLMN broadcasted by the target cell from the ECGI, e.g. D, but D is not the accessible rPLMN or ePLMN of the UE, and thus the source eNB can not perform the handover procedure. This problem also exists when the target cell is the hybrid cell and supports multiple PLMNs. The source eNB originally selects a hybrid cell under a PLMN of which the UE is the member, but because of the above problem, it is possible that the source eNB selects a hybrid cell under a PLMN of which the UE is not the member, and thus the UE can not enjoy better service quality and accounting strategy.
Even if the source eNB knows the PLMNs broadcast by the target eNB cell, the source eNB needs to select a new registered PLMN of the UE from PLMN{C} according to the PLMNs {D, A, C, E} broadcasted by the target cell and the accessible PLMN{B, A, C} of the UE. But the source eNB does not know the PLMNs of which the UE is the member, if the source eNB selects the PLMN C, the handover will fail. If the target cell is the hybrid cell or supports multiple PLMNs, the source eNB may select any PLMN, but the following problem is produced. The UE originally can access a PLMN of which the UE is the member, e.g. (c1, A), but the source eNB makes the UE access the PLMN of which the UE is not the member, e.g. (c1, C). Therefore, the UE can not enjoy good service quality and accounting strategy.
In order to solve the above problem, in one mode, the UE firstly filters out such PLMN: the PLMN is in the PLMNs broadcasted by the target cell, is the rPLMN or ePLMN of the UE, the PLMN ID and the CSG ID are in a list of accessible CSGs of the UE. The UE sends the filtered out PLMNs to the source eNB via a measurement report; the source eNB selects the PLMN which is the rPLMN or ePLMN of the UE from the PLMNs reported by the UE. The source eNB sends the selected PLMN and a CSG identification of the target cell to a source SGSN/MME, and the SGSN or MME performs a final member authentication.
But when the UE is in a CS field, there is no location area update procedure for the UE in a connection mode, The UE can not obtain the updated rPLMN or ePLMN in time. Therefore, after the UE performs the filtering according to the above principle, a current accessible PLMN of the UE may be not obtained, and thus the problem can not be solved correctly.
In addition, when the target CSG cell does not support the RAN share, because the UE in the CS field can not obtain the updated rPLMN or ePLMN in time, when the UE performs primary access control, the UE which is the member may be incorrectly determined as a non-member. If the UE reports a non-member identity to the source RAN, the source RAN will not initiate the handover procedure to the target cell, and thus the UE can not access the HeNB of the UE.